...or for that matter, what didn't it do, so that you'd use the "bootloader/main program" separation instead of loading everything at once.
Normally, when loading games or any non-BASIC software from tapes, you'd start the computer holding START+OPTION - it disabled BASIC ROM and started it in 'boot' mode. A characteristic deep beep sounded, you'd press 'play' on the cassette recorder, then Return on the keyboard. Some 8-10 seconds of high-pitched constant lead-in, then six (very rarely any other number) records of data from the tape, another deep beep, and another lead-in. At that point often the screen would change, to show some countdown, ads, welcome, or whatever extras the bootloader contained. The game proper would begin loading, and start when it finished loading.
I never understood the waste: obviously the bootloader was a program, and often quite fancy one. Why couldn't the whole game be implemented as a bootloader? Why waste time on the two start-up procedures, two lead-ins, and a piece of software that was usually overwritten by the game when it finished loading? What were the shortcomings/restrictions of the bootloader so that it was universally implemented in such a minimal form, instead of just being the full application/game?
EDIT: Just to clarify:
- about the most common, generic bootloader didn't print anything or affect the screen in any way.
- you couldn't just fast forward past the bootloader and start from the game proper. It wouldn't load, generating a 'BOOT ERROR' message instead.